Method of decorating ceramic bodies



Patented Feb. 26, 1952 UNITED sTATEs PATENT OFFICE METHD OF DECORATING CERAMIC BODIES Richard -B. Harlan, Long Beach, and Walter E.

Gardnen Whittier, Calif., assignor s, by mesnel assignments, to Ceratile' Corporation, Paramount, Calif., a corporation o'f 'California Application January 7, 1949, Serial No.=69,644 6 Claims. (c. rrr-40) The present invention relates to a 'method and means whereby ceramicbodies of any character, specically by way of example, tile, may be surface decorated, the decoration'being in the glaze.

With our method, various decorative efiects maybe obtained which add to the beauty of the tile in that the surface' of the `tile may be in 'We have discovered that a glazed design may h'applied 'to a ceramic body followed by applying a further glaze or a background glaze thereover, which glazes after glost firing will not materially ruse or run together, but tend to separateso as to produce unusual eects, although predetermined, in the glaze decoration.

We are aware that prior to our inv ention, var

.ious'methods have been utilized in the art to decorate ceramic bodies, among which may be mentioned the adding of coloring oxides .to the glaze; the so-called underglaze method which 'utilizes slip painting or undergla'ze colors, and sometimes underglaze decalcomania; the overglazemethod which utilizes overglaze colors and overglaze decalcomania, and the inl'ay method which. utilizes full glazes applied .by hand.

Those skilled in the art to which this invention belongs, will recognize these different methods now 'in use for the decoration of ceramic articles and the difficulties attendant in such decoration.

Briefly some of these difficulties are as follows:

in overglaze work three firings are necessary and overglaze work is not durable'or wear-resi'stant; in underglaze work deep rich 'colors are not easily obtained and of a necessity the 'glaze used must be transparent, and the inlay method is done by hand which is expensive, and results in ununiformity on work. i A further object of our invention is 'a decoratlon method for ceramic articles which is inexpensive in actual practice, does not of necessity require skilled labor, wherein uniformresults are attained, and whichis simple to practice. Furthermore the glaze decoration is durable and war resistant, and all the beauty of the de ign isprserved.

Inthe drawing i Figure 1 is a section of aplain tile; V w

Figure 2 is a sectional View of the tile of Figure 1-,-with a glazed design applied thereto; p

Figure 3 is the tile of Figure 2 with a 'background .glaze appled over the, design glaze and the surface of the tile; and

Figure .4 is sa sectional View showing the ap pearanceof thedesign glaze, and the background glaze after glost firirg. y

Primarily for the purpose of the present inven tion, we have assumed a classification 'for glazes. Searle in The Encyclopaedia oftheCeramic Industry states as to glazecompositions; (1) glazes .are. often .divided 'broadly into lead glazes and leadless glazes, ,and they may be Classified according to their composition, i. e. as to the nature of the flux; (2) the alumina to silica ratio 'or the acid to baseratio; and (3) the acidity number or acid equivalent 'We accept this classification for an understan'ding of 'the present invention and it 'is adopted for the reason that the same classifica'tion is used for g'lass. We, therefore, for the purpoeof llustrating our invention, classify the gla'zesinto our types: n

The above listed types 'of glaz'es are well known to those skilled in the art and constitute recognized glaze types. By referring to "An Encyclopaedia of the Ceramic Inlustries'? by Searle, published 1930, We find in Volume Il on pages 25 1 and 252 and also on page 248 under the title Lead glaze" a discussion of the lead silicate glazes, and as this publication indicates the lead silicate glazes compriseessentially a mixture of lead oxide and silica. The proportions of the materials may vary throughout extremely wide ranges, there being substantially no limit. Some compositionshaving as low as 1% silica are described and the article indicates that the quantity of silica varies the melting point. The publication clearly shows thatthe ratio of lead oxide to silica merely affects the refractoriness and softenng temperatures of the glaze. On page 248`the publication states: f The use of a suitable proportionof lead in a glazehas the following results: (a) It makes the molten glaze mobile, so that it flows easily over the surface of the Ware and produces a more 'uniform coverage than a less mobile glaze; (b) It produces a glaze of high refractivity and therefore imparts greater lustre; (c) It produces glazes having so great a range of fusibility that small variations in the composition of the glaze are of much less importance andare far less likely to cause trouble than When ;ma lead is present. This article furthei* states; f'Th'e' a'ddition of silica, alumina,

lime, potash, etc. raises the melting point of the glaze and. makes -a harder produc Also in Volume II on page 250 the author describes the effect of changes in proportion of lead oxide on the maturing time and points out that an excess of sil'ca or alumina will raise the melting point.

The second t pe of glaze described above namely, lead-boro-silicates. are discussed on page .1.13 of Volume I of the Searle Encyclopaedia. Under the definition of Boracic azes. Searle states that the lazes containing boric oxide may or may not contain lead oxide also. Those glazes containing both boric oxide and lead oxide are commonly referred to as lead-boro-silicates (see technological naoers of the Bureau of Standards, No. 31, publ shed 1914:, page 4).

The alkali-boro-sil cate tybe of glaze is dis cussed in Searle, Volume II, page 252 under "leadless glazes" and defines those glazes contain'n no lead ox de but containing alkali oxides instead. The article states' that these glazes may have their fusibility regulated by the addition of borax. boric acid, soda or potash. The alkali lazes containing boric acid are the alkaliboro-slicate z s contennlated hv an licant.

Pa e 113 of Vo ume II of the Searle Encyclonaedia defines alkaline-calcerous glazes, which is the glaze identified herein as the alkali-limesilicate glaze type 4 above. identifles a grou of such calcareous glazes in wh ch the flux is lime.

Throuhout the entire published literature and 'oarticularly that identified above the art reco n zes the classifications heretofore set forth and clearly shows that it is within the skill of the art to compound glazes within those classifications. It is well within the knowledge of the art that the materials constitutin each type must be present in significant ouantities and. as the literature indicates, the relative nroportions vary certa n characteristics of the glaze, all as is well. known. Throu hout this ap lication and claims it is to be understood that identification of any one of the ty es refers to glazes comprising essentially substantial pro ortions of the named ingredients in the oxide form.

l.. Lead-silicate lazes.

2. Le d-boro-sil ate glazes. 3. A kali-boro-silicate glazes. 4. Alkali-lime-silicate glazes.

We make use of this glaze classification, in the practice of our invent on and wherein we utilize a glaze of one classification as the design glaze, and a glaze of another classification for the back round glaze. In other words, we may utilize one or more glazes in the same classifica- 't on as des n glazes, and a different t ne of gl 'te for the back round. This holds true at all times in the practice of our invention. Hence, e may utilize one' or more types of glazes for the desi n provided a different type of glaze is used for the back round. If glazes of the same tyne are in contact. the glazes may run to ether.

The glazes may be :orenared in ariy usual manner, such as by ball m ling the materials used i the ,glaze com osition with' water. One method which we have em loyed is to dry out the desi n glaze or glazes to be used. and then susnend the laze in an oil medium followed by nassing the glaze through a color mill to insure homo eneity.

Referring to the drawing. assumng a design glaze of oneof the glaze tynes previously mentioned, the design 'may be applied to the ;sugiag of the ceramic article, specifically the tile by passing the design glaze through a coarse silk screen carrying the desired design. The design glaze may also be applied by brushing or spi-aying or by any other common method of applying a glaze to a ceramic article in the form of a design. After the design glaze has dried at room temperature, the background glaze may be dipped or sprayed over the surface of the tile and the design glaze, as shown in Figure 3. Thereafter, the tile is glost fired. Drying of the design glaze before application of the background glaze is desirable for handling reasons, although such procedure is not necessary if care is exercised.

The background and design glazes mature in the same temperature range or in an overlapping temperature range. Thercfore, the method of our nvention is limited in temperature only to the extent that specified types of glazes can be used together. By Way of example and not in limitation of the invention, an upward firing limit of glazes containing either lead or boron. or both, is approximately Seger cone 5, or about 1190 C. (2l74 F.). The lower limit of an alkali-lime-siiicate glaze is Seger cone 1, or about 1100 C. (2012 E), and an alkali-boroi silicate g1aze,cone 014 or 815 C. (about 1500 F.)

Under (D) Searle The lower limit for the lead and boron glazes is approximately Seger cone 08 or about 945 C. (1733 F.). The upper limit for the alkalilime-silicate glaze is about Seger cone 3 or about 1145 C. (2093 F.), and the upper limit for an alkali-boro-silicate glaze is about seger cone'02, or about 1095 C. (2003 F.).

We have found that if the design glaze is more fiuid or has less viscosity than the background glaze, the background glaze will readiiy flow or separate from the design glaze during the glost ring, due to the lessening of the surface tension between the two glazes. Hence, the viscosity of each glaze is utilized as a means of controlling the degree of separation therebe tween. This separation is illustrated in Figure 4 and wherein the design glaze is shown at I, and the background glaze at 2, the background glaze having separated from the design glaze, as shown at 3. This separation is quite marked in actual practice. The viscosity of the glaze may be controlled by the alumina content there of or by increasing the refractoriness of the glaze by the addition of refractory oxides, such as magnesium oxide, calcium oxide, and others'. This latter method affects the maturing temperature of the glaze, but so long as the maturing temperature of one glaze is within the maturing range of the other glaze, satisfactory results are obtained. Obviously, the viscosity may be lessened by the addition of more fiuxing oxides in the glaze composition.

The Searle Encyclopaeda previously identified, in Volume II on pages 114 and 115 describes at some length the efiects of alumina in glazes and indicates that the addition of alumina to a glaze composition has the efiect of increasing its viscosity.

We have found that the thickness of the application of the glazes is of importance, and that the design glaze should not be appreciably thicker than the background glaze. In practice, the range of thickness for the design glaze may be from 3 to 20 thousandths, while the background glaze may vary from 5 to 25 thousandths. To'

obtain embossed design effects, the design glaze may be one-half as thik as the background As an illustration of formulasfor design and background glazes which may be utilized, we give ;the following examplesz #1. Design glaze-(lead-boro-silicate typel Maturing range -cone 07 to .05

.175 NaKO` .522 BzOa .162 Cao .123 FezOs .575 PbO '2,98 .350 SnOe .087 cuo 1,905 SO2 #l-B. Background glaze (alkali-boro-silicate) Maturing range--cone 06 to 04 .7330 NaKO .1775 ZnO .375 A12O3 .109 ZrOz 0.22 SbzOs .080 NaF .8905 2.64 SOz #3. Design glaze (lead-boro-silicate type) Maturing range-cone 1 to 5 .049 A12O3 .921 SiOz .328 AlzOB 2.15 SO2 .523 3203 .337 ZrO .125 NazO .250 '3203 2.060 SiOz .047 KzO '300 Zno .198 A1203 .070 CuO .248 PbO #s-B. Background az (alkali-lime-silicate) Maturing range (cone 1 to 5). .135 NazO .272 CaO .693 cao .266 3203 .232 KzO 33405102 .049 ZnO .354 ZrOz By referring to "ceramic Glazes" by Cullen W. Parmelee, published in 1948, there will be found beginning on page 6 thereof a discussion of opacifiers and identification of the various materials commonly employed for such purpose. The chapter beginning on page 268 of Parmelee discusses coloring materials and identifies the various materials commonly used for imparting various colors to glazes.

The Parmelee publication, beginning on page 6 thereof. It will .also ibe .apparent to those skilled in .the tartthat :the :examples contain opacifiers and coloring oxides.

Attention is called to the'fact ?that where 'we have .designated one glaze .as "design" and the other glaze as background? that these designa'tions maybe reversed as long as the principle of the invention, as outlined heretofore is followed.

'The ceramic 'bodies may *be decorated rapidly and :uniformly :by one operator applying the design glaze, followed by a second operator applying thereover, after the design glaze has dried, the 'background glaze by spraying or any other method. 'This results in the so-called straight line application of glazes and is rapid and economical from a labor standpoint. Given glazes of definite classes with a given firing temperature, the results are always the same and the tile so treated will be substantially uniform in design and color. It is a feature of the invention that the separation of the glazes occurs without any noticeable irregularity during the A glost firing. Each piece of tile or other ceramic article will have an almost identical fired appearance with another tile of the same type providing it is treated in the same or a like manner.

We claim: l. In a method of producing decorated ceramic clay articles, the steps of applying a first alumina-containing glaze-forming composition to' selected portions of a surface of said article, said composition having sufcient solids to form a substantially uniform layer of solids of a thickness of from 3 to 20 thousandths of an inch before firing, thereafter applying a continuous layer of a background glaze-foi-ming composition containing alumina over said first layer and uncoated portions of said surface, said background layer having suflicient solids to form a substantially uniform layer of solids of a thickness of from 5 to 25 thousandths of an inch before firing, and simultaneously glost firing said first and background compositions on said article; each of said first and background compositions being selected from the group consisting of: (1)" a leadsilicate glaze consisting essentially of substantial proportions of lead oxide and silica, (2) a lead-boro-silicate glaze consisting essentially of substantial proportions of lead oxide, boron oxide and `si1ica, (3) an alkali-boro-silicate glaze consistng essentially of `substantial proportions of alkal metal oxides, boron oxide and silica and 4) an alkali-lime-silicate glaze consisting essentially of substantial proportions of alkali metal oxides, calcium oxide, and silica; said first and background compositions each being a, different i one of said group and said first composition 125, also discusses the effects of the addition of c having substantially less alumina than said background composition whereby during glost firing said background composition developes a fluid state of lesser fiuidity than that of said first composition and withdraws therefrom without substantial difiusion thereinto to uncover said first composition on said selected portions, both said compositions having overlapping maturing temperature ranges and said glost firing being carried out within said overlapping ranges.

2. A method as defined in claim 1 wherein said first composition contains ceramic pigmenting materials.

3. A method as defined in claim 1 wherein said first composition contains ceramic pigmenting materials and wherein said background composition contains opacifying materials.

4. A method as defined in claim 1 wherein said first composition is a lead-boro-slicate glaze and REFERENCES CITED Whorein Sam background composition 15 an The following references are of record in the alkali-boro-silicate glaze. p me of this patent;

5. A method as deflned in claim 1 wherein 5 said first composition is a. lead-slicate glaze `and UNITED STATES PATENTS wherein said background composition is a lead- Number Name Date boro'smcate glaze- 488,(383 Vo11rath Dec. 27, 1892 6. A method as defined n claim 1 wherein 529 670 stewart Nov 20 1894 said first composition is a lead-boro-silcate glaze 10 23193376' Homme 1935 and wherein said background composition is an alkali-lime-siicate glaze.

RICHARD, B; HARLAN. WALTER. E. GARDNER. 

1. IN A METHOD OF PRODUCING DECORATED CERAMIC CLAY ARTICLES, THE STEPS OF; APPLYING A FIRST ALUMINA-CONTAINING GLAZE-FORMING COMPOSITION TO SELECTED PORTIONS OF A SURFACE OF SAID ARTICLE, SAID COMPOSITION HAVING SUFFICIENT SOLIDS TO FORM A SUBSTANTIALLY UNIFORM LAYER OF SOLIDS OF A THICKNESS OF FROM 3 TO 20 THOUSANDTHS OF AN INCH BEFORE FIRING, THEREAFTER APPLYING A CONTINUOUS LAYER OF A BACKGROUND GLAZE-FORMING COMPOSITION CONTAINING ALUMINA OVER SAID FIRST LAYER AND UNCOATED PORTIONS OF SAID SURFACE, SAID BACKGROUND LAYER HAVING SUFFICIENT SOLIDS TO FORM A SUBSTANTIALLY UNIFORM LAYER OF SOLIDS OF A THICKNESS OF FROM 5 TO 25 THOUSANDTHS OF AN INCH BEFORE FIRING, AND SIMULTANEOUSLY GLOST FIRING SAID FIRST AND BACKGROUND COMPOSITIONS ON SAID ARTICLE; EACH OF SAID FIRST AND BACKGROUND COMPOSITIONS BEING SELECTED FROM THE GROUP CONSISTING OF: (1) A LEADSILICATE GLAZE CONSISTING ESSENTIALLY OF SUBSTANTIAL PROPORTIONS OF LEAD OXIDE AND SILICA, (2) A LEAD-BORO-SILICATE GLAZE CONSISTING ESSENTIALLY OF SUBSTANTIAL PROPORTIONS OF LEAD OXIDE, BORON OXIDE AND SILICA, (3) AN ALKALI-BORO-SILICATE GLAZE CONSISTING ESSENTIALLY OF SUBSTANTIAL PROPORTIONS OF ALKALI METAL OXIDES, BORON OXIDE AND SILICA AND (4) AN ALKALI-LIME-SILICATE GLAZE CONSISTING ESSENTIALLY OF SUBSTANTIAL PROPORTIONS OF ALKALI METAL OXIDES, CALCIUM OXIDE, AND SILICA; SAID FIRST AND BACKGROUND COMPOSITIONS EACH BEING A DIFFERENT ONE OF SAID GROUP AND SAID FIRST COMPOSITION HAVING SUBSTANTIALLY LESS ALUMINA THAN SAID BACKGROUND COMPOSITION WHEREBY DURING GLOST FIRING SAID BACKGROUND COMPOSITION DEVELOPES A FLUID STATE OF LESSER FLUIDITY THAN THAT OF SAID FIRST COMPOSITION AND WITHDRAWS THEREFROM WITHOUT SUBSTANTIAL DIFFUSION THEREINTO TO UNCOVER SAID FIRST COMPOSITION ON SAID SELECTED PORTIONS, BOTH SAID COMPOSITIONS HAVING OVERLAPPING MATURING TEMPERATURE RANGES AND SAID GLOST FIRING BEING CARRIED OUT WITHIN SAID OVERLAPPING RANGES. 